Abrasive wheel



Feb. 23, '1937. E. VAN DER PYL 2,072,051

ABRAS'IVE WHEEL Filed Aug. 12, 1955 EDWARQ VAN DER F'YL.

Patented Feb. 23, 1937 ABRASIVE WHEEL .Edward Van der Pyl, Holden; Mesa,assignor to Norton Company, Worcester, Mass, a corporattion ofMassachusetts Application August 12, 1935, Serial No. 35,881

t Claims.

' The invention relates to abrasive wheels and a method of making thesame.

One object of the invention is to provide a low melting point metallicbond for diamonds. An-

. other object of the invention is to provide a grinding wheel forgrinding very hard substances.

Another object of the invention is to provide a grinding wheelcomprising very hard grain and a bond suitable therefor. Another objectof the invention is to provide a bond for diamond abrasive from whichthe diamonds may be recovered at small expense and without destructionof the diamonds. Another object of the invention is to provide a methodof bonding carbonaceous grain which is effective and which may becarried out without burning the grain. Other objects will be in partobvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, and in the severalsteps and relation and order of each of said steps to one or more of theothers thereof, all as will be illustratively described herein, and thescope of the application of which will be indicated in the followingclaims.

In the accompanying drawing, in which is shown one of various possibleembodiments of the mechanical features of this invention,

Fig. 1 is a plan view of a grinding wheel con structed in accordancewith certain features of the invention,

Fig, 2 is a cross sectional view on the line 2-2 of Fig. l.

According to the preferred method of carrying out my invention, Iprovide diamond grit in finely divided or grain form. Diamond gritwhich, because of its extreme hardness and its other qualities,constitutes probably the best abrasive substance known, exists in a formcommercially known as bort" which iscommercially available in sumcientquantities and at such prices that it may be used for .the manufactureof grinding wheels and other abrasive bodies. While bort is expensive,nevertheless on account of the great 5 superiority of the diamond forabradant purposes, the wheel formed thereof has many practlcal uses andadvantages.

Also, in the preferred embodiment of my invention, I provide bond in theform of a powdered lloy. Although such powdered bond might be a mixtureof two or more metallic'powders, I prefer to proceed as follows.

Selecting two or more metals according to conslderations hereinafter setforth I put them tomssun gether in a melting pot in the proportions de-,sired and melt them together. I then cast ingots of the alloy in sandmolds. These ingots I then crush by means of crushing rollersor the likeuntil the alloy is in powdered form of the desired mesh size. a

With the powdered metallic bond of the type indicated I mix in theneighborhood of between 25% and 50% by volume of diamond bort in a gritsize of between mesh and 500 mesh, ion

example. Mesh size of the bort selected will de-Y Y pend upon theabrading operation that the wheel is to perform, arid my invention hasno limitations in this respect, in; so much as grinding, polishing andlapping operations differ vastly among them= selves. For the finerpolishing or lapping operations, finer grit size of bort will be used.The mesh size of the metallic bond may also vary between wide limits; Imerely note that using mesh diamond grit, powdered bond of 200 mesh ishighly practical, but other mesh sizes of the bond may be used even withthe given size of diamond grit.

The mixing of the grit with the bond may be accomplished manually, foralthough machine methods might be used, the bort or diamond dust is sovaluable as to dictate care in the mixing to avoid loss of diamond.Setting apart a measured or desired quantity of mixed bond and bort, I

place it in a mold. This mold may take any form.

for although I am describing the invention in connection with themanufacture of a wheel, other abrasive bodies are to be deemed included.In case the abrasive body is a wheel, in most cases it will have acentral hole for mounting upon an arbor or the 1ike,"and accordingly insuch cases the shape of the mold is an annulus. For the material of themold I prefer graphite, on account of its many desirable properties,such as, that it may be easily destroyed to remove theformed wheel; ithas an afiinity for oxygen thus inhibiting oxidation of the materials ofthe wheel; it is reasonably inexpensive; it may be easily machined intodesired form or shape; it will not melt and will not go to pieces underany temperatures which I contemplate. using.

Having placed the desired quantity of mixed grain and bond in the moldselected, I apply heat and pressure. Within the limits of my inventionthe pressure range is wide, and the heat employed is such as to causesintering of the bond at the pressure employed or under the conditionsof intimate union achieved. For example, I may cold press the bond andabrasive grain, heating the substance thereafter. In such" cases I-might use a mold other than graphite hr connection with 55 plunger andpressure mechanism, heating the formed or green wheel on a bat". Theunion of the metallic grain after. it has been pressed is such that itmay be formed into a practically in- 5 tegral mass lwhich will tightlyhold the abrasive bodies by heat treating at a temperature which doesnot completely melt to a' liquid state but per. With the copper I alloyanother metal which produces an alloy harder and more brittle thancopper. I desire the bond to holdthe diamonds firmly, to be tough enoughso that the diamonds will not rip out, and nevertheless at a certainpressure and resistance to go to pieces rather than glaze. It isdesirable that the bond should crumble of! in little bits or linefragments so as toexpose new cutting edges of the diamond from time totime, and an alloy or metal which can be crushed to powdered form mayhave the desired characteristics. I give below examples of specificalloys which I may use.

Example Ie-I form an alloy of 68% copper and 32% tin. This alloy is abronze having brittle characteristics. Although the exact proportionsindicated need not be employed, nevertheless I prefer to use somethingaround these proportions as this is a fairly critical range andsubstantially difierent pro rtions of copper and tin do not 35 have thesam characteristics. This alloy melts at 750 C. and enables me to sinterit at a temperature at which there is very little danger of oxidizingthe diamonds. Example 2.I make an alloyof copper and nickel, 35-50% ofcopper and 65-50% of nickel. This also has brittle characterics and istough.

It melts at around 1200 C., but I may use the precautions hereinafterreferred to to prevent oxidation of the diamond or the bond.

Example 3.-I make an alloy comprising approximately 85% copper with 15%aluminum. This melts at around 1050 C. and has brittle characteristicsbut is fairlytough. y 4

Example 4.I make an alloy of copper and manganese, 65% or more of copperand 35-20% of manganese. This melts at 900 C. and has the properties oftoughness and brittleness desired.

Example 5.I use nearly pure copper but mix in with it a very smallproportion, from a trace to\1% or 2%, of beryllium (glucinium). Coppermelts at 1065 C. or thereabouts.

It is advantageous to take certain precautions against burning of thediamonds in the case of the alloys which sinter at the higher tem-'peratures, for example above 900 C. The use of a graphite mold orcontainer during the heating operation is such a precaution. However,even when a graphite mold is used, and more especially so when it isnot, it will be well to heat the body in a non-oxidizing atmosphere,such as nitrogen or hydrogen. I havealso found that a small amount ofaluminum, silicon or magnesium may be introduced into the bond,preferably as separate distinct metallic particles, that is not in analloy state,- which will inhibit oxidation of diamond and bond becausesuch metals have a great aflin-' ity for oxygen.

In many cases I desire to make the bond as '75 brittle as possible forthe specific alloy used and brittleness is enhanced by quenching theabrasive body when still hot from the heat treatment. One markedadvantage of a wheel constructed according to the invention lies in thefact that, when produced in-annular form, it may be readily 5 /united toa. central disk. Diamond grinding wheels are, under present marketconditions, expensive, whatever the bond used, owing simply to the highprice of bort, and accordingly it is highly desirable'to waste as littleof the diamond 10 as is possible. In the case of any grinding wheelwhich is thin relative to its diameter, the central part will generallynot be used for abrading. Accordingly, in the case of diamond wheels itis preferred to form the central part in the form of 15 a non-grindingdisk or annulus. While a small internal grinding wheel, having a lengthon the. order of half its diameter, may comprise grinding substance andbe attached by mounting directly upon a spindle, in the case of acutting- 20 off wheel or a large sized wheel for the grinding of thecemented tungsten carbides and other hard substances, it is generallyfound economical to secure what amounts to an annular band of diamondgrinding material to a central disk having 25 a hole therein. Therefore,a distinct problem has arisen in attaching the inside of the annularband of grinding substance to the periphery of the central supportingdisk. If the union between the parts is weak, fracture will result andthis 30 destroys the grinding wheel which may have a market value in theneighborhood of from $50 to $200.

According to the present invention, with diamo .ld bonded with metallicbond as disclosed in 35 the foregoing description, I may provide a thinaluminumdisk, or a disk of any other metal, and form my grindingsubstance inthe shape of an annular band whose inside diameter is thesame as the outside diameter of the disk. I may then 40 unite the diskto the grinding band by brazing, soldering, preferably with silversolder, or by any other metallurgical operation for integrally unitingmetals, such as welding or the like, and the result is an integralstructure of central support- 5 ing metallic disk having an annular bandof grinding substance on its periphery including diamond grain bonded ina metal bond. For cutting-oil wheels and the like, the centralsupporting disk should be no thicker than the annular 5o band ofgrinding material. Referring now to the drawing, Iprovide a central diskIII which may be made of any suitable metal, such as aluminum. Accordingto any of the methods hereinbefore disclosed I form an abrasive annulusll whose 55 inside diameter is the same as the outside diameter of thedisk I0. I then attach together the disk in and the annulus II by meansof silver solder l2 or otherwise in accordance with the foregoing.Desirably the disk 10 has a central 0 hole l3.

Although I have noted throughout diamond as the abrasive grit, certainadvantages inhere in the combination of the bond specified with boroncarbide grit. Boron carbideis an expensive abrag5 sive grit, althoughnot as expensive as diamond bort. Furthermore, boron carbide as well asdiamond should not be exposed to high temperatures, or if it is only fora short time and with suitable precautions such as indicated, in orderto avoid 7o oxidation and other chemical changes. The bonds describedherein are all of them reasonably low melting point bonds. and they fuseor sinter at a somewhat low temperature when under pressure or when theparticles are in intimate con- 1 tact as described, and accordinglythese bonds are very suitable for the bonding of diamond and othercarbonaceous substances such as boron carbide. The bonds of theinvention are more in the nature of a matrix than the common vitrifiedbonds, and they are harder and tougher than the artificial resinousbonds, and have properties dif ferent from those of a rubber bond, andthe properties of the bonds of this invention are highly desirable incombination with grain of extreme hardness such as diamond and boroncarbide, on Mohs scale extension I5 and I4 respectively.

It will thus be seen that there has been provided by this invention amethod and an article of manufacture or composition of matter in whichthe various objects hereinabove set forth together with many thoroughlypractical advantages are successfully achieved. As various possibleembodiments might be made of the mechanical features of the aboveinvention and as the art herein described might be varied in variousparts, all without departing from the scope of the invention, it is tobe understood that all matter hereinbeiore set forth is to beinterpreted as illustrative and not in a limiting sense.

I c1aim:--

1. An abrasive body comprising diamond grain and a copper nickel bond.

2. An abrasive body comprising diamond grain and a copper aluminum bond.

3. An abrasive body comprising diamond grain and a copper manganesebond.

4. ,An abrasive body comprising diamond grain and bond consisting ofcopper and an additional element imparting brittleness to the copper.

5. An abrasive body comprising diainondgrain and a metallic bondconsisting of copper and an additional metal adapted to impartbrittleness to the copper and comprising one of the group consisting oi'nickel, aluminum and manganese, the

proportion of the additional metal being such as will impart thebrittleness.

6. A grinding wheel comprising a metal disk integrally united to anannular outside band comprising diamond grain bonded with metal, boththe disk and the band including aluminum.

EDWARD VAN DER PYL.

